Phase contrast microscopy was invented in 1935 by Zernike, and enables objects which typically only change the phase of radiation, compared to the surroundings of the object, to be seen. The phase contrast microscope devised by Zernike converts object phase changes into amplitude changes in a final image of the object, thus allowing phase details of the object to be seen. Since its initial invention, there have been a number of systems which claim to have improved microscopy in general, as well as phase contrast microscopy.
U.S. Pat. No. 6,937,343 to Feldman, whose disclosure is incorporated herein by reference, describes a method for optical evaluation of a sample by scanning a beam of coherent radiation over the sample. A frequency shifted reference beam is generated from the scanning beam, and the reference beam is combined with scattered radiation from the sample to generate an optical heterodyne signal characteristic of the sample.
U.S. Pat. No. 7,002,695 to Feldman, whose disclosure is incorporated herein by reference, describes apparatus which includes a source generating a coherent radiation beam, and traveling lens optics which focus the beam to two spots on the surface of a sample. Interference fringes are generated from radiation collected from the two spots, and changes in the fringes may be used to assess optical characteristics of the sample.
U.S. Pat. No. 3,851,951 to Eveleth, whose disclosure is incorporated herein by reference, describes a laser system in which light is focused upon an image plane by interaction with frequency modulated acoustic pulses in a Bragg cell. The light is scanned across the image plane in accordance with the movement of the pulses along the cell.
Published International Patent Application WO 2004/042433 to Rietman et al., whose disclosure is incorporated herein by reference, describes programmable lenses and gratings which are claimed to be of use in a variety of optical applications.
U.S. Patent Application 2006/0256350 to Nolte et al., whose disclosure is incorporated herein by reference, describes apparatus for assessing topology of a surface of a target. The apparatus includes an optical source for generating a probe laser beam, and also includes means for scanning the probe laser beam across at least a portion of the surface of the target.
U.S. Patent Application 2005/0057727 to Troyer, whose disclosure is incorporated herein by reference, describes a laser projection system. The laser beam is modulated using a reflective liquid-crystal light valve.